Better designed clinical research needed on lipid-based eye drops for DED
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Key takeaways:
- Data suggest that lipid-based eye drops have potential to treat evaporative dry eye disease.
- Several reviewed studies did not have a control group, making it difficult to determine whether lipids are effective.
Lipid-based eye drops may help treat evaporative dry eye disease, although additional research, particularly with placebo-controlled study designs, is needed, according to a review.
“Combining lipid-based eye drops with conventional treatments like cyclosporine or diquafosol, omega-3 supplementation or lid wipes may also potentially improve the management of evaporative dry eyes,” Farqan A. Maulvi, PhD, from the School of Optometry and Vision Science at the University of New South Wales, and colleagues wrote in Contact Lens and Anterior Eye. “Researchers and eye care health companies are continuing to explore new approaches to developing innovative lipid-based eye drops to address this unmet medical need.”
According to researchers, patients with meibomian gland dysfunction may benefit from therapies that promote a thicker lipid layer and therefore greater stability of the tear film.
Currently available lipid-based eye drops mimic aqueous and lipid layers of the tear film, using mineral oil, castor oil, phospholipids, omega-3 fatty acids and triglycerides. Ingredients such as glycerol, trehalose and certain amino acids protect the ocular epithelium from the hyperosmolarity effect of tear evaporation.
To provide an overview of commercially available lipid-containing eye drops, Maulvi and colleagues searched PubMed and Google Scholar to identify relevant clinical studies published between 1995 and 2023.
According to researchers, formulations using mineral oil are designed to spread across the ocular surface to reform the mucoaqueous layer, which is hypothesized to help replenish the lipid layer during normal blinking.
In a phase 4 study of dry eye patients, those who used eye drops with a nanoemulsion of mineral oil daily for 28 days demonstrated small but immediate improvement in burning and stinging symptoms for up to 8 hours. When those drops were used twice daily, the participants demonstrated an insignificant increase in tear breakup time and improvement in ocular discomfort. Studies examining these drops for contact lens discomfort found that they could alleviate discomfort, but in one study with a placebo group there was no significant improvement.
There is evidence that castor oil may help restore the lipid layer of the tear film and alleviate dry eye and contact lens discomfort, but most clinical studies lacked a control group.
Eye drops containing omega-3 fatty acids were associated with stabilizing the tear film in patients with meibomian gland dysfunction, indicating they may be effective in treating evaporative dry eyes.
A study of liposomal spray found that participants’ comfort improved by 46% after 30 minutes of treatment compared with 18% with saline treatment. Another randomized study found that liposomal spray had particular benefits for patients with a thinner baseline lipid layer.
“Although the available data suggest some potential for lipid-based eye drops to successfully treat evaporative dry eyes by enhancing the structure and thickness of the lipid tear film, there is still a need for further innovation in this area, as well as better designs for clinical trials,” Maulvi and colleagues wrote.
A number of the studies were not placebo-controlled.
“This is important, as changes could have been due to other excipients in the formulations or, indeed, just adding extra volumes of buffered solutions to the eyes,” they concluded.
Perspective
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This recent review article provided a concise and informative update for clinicians based on available high-level research on the efficacy of different lipid-based eye drop formulations for the treatment of evaporative dry eye disease.
The available evidence suggests some potential for lipid-based formulations in improving the thickness and stability of the tear film, thereby relieving symptoms and signs of dry eye disease, particularly in patients with meibomian gland dysfunction. However, the strength of evidence varies for different formulations, which affects the confidence with which we can make recommendations to patients.
Major limitations in the available research are the lack of placebo-controlled studies to specifically evaluate the therapeutic benefit of the lipid ingredient in these formulations and the lack of studies comparing lipid-based formulations with each other. Considering that a common concern from patients is the short-lived symptomatic relief from artificial tears, further research on the long-term effects of these formulations is also crucial.
Given that tear film stability is not only affected by lipid layer thickness but also tear film composition, further research is warranted to understand how the application of lipid-based eye drop formulations can improve the composition and biophysical properties of the tear film, which can guide the development of ocular lubricants that have longer-lasting effects.
Clinicians should continue to stay informed regarding the research and innovation in this area of therapeutic options for patients with evaporative dry eye.
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